Traditionally, these operability specifications are defined using Response Amplitude Operators (RAOs), which predict a vessel’s response under various wave conditions. While RAOs have been a cornerstone of naval architecture for decades, the question is becoming louder by the day: Is this old-school method still the best we can do, or is it time to upgrade to a new paradigm in real-time vessel motion analysis?

1. How Vessel Operability Specs Are Currently Written Today?

a. Predictive Curves & Operational Envelopes

Naval architects run wave-basin tests or computational simulations to generate RAO curves. These curves describe the vessel’s expected motion—heave, roll, pitch, surge, sway, and yaw—across a range of wave heights, periods, and directions.

b. Design Conditions & Assumptions

RAOs hinge on the vessel’s “design condition”—ballast, cargo load, distribution, and sea-state assumptions that might be radically different from what happens in real-time.
This inherently static approach can lead to over-conservative or, in some cases, dangerously optimistic specifications.

c. Safety Margins

Because RAOs are theoretical models, large safety margins are often layered onto these specs.
While this is good for reducing risk, it can also shrink operational windows, causing project delays and lost revenue.

 

2. The Cracks in the RAO-Only Approach

a. Limited Adaptability

Vessels are dynamic systems—cargo changes, ballast configurations shift, and real sea conditions rarely match the average or “typical” scenarios used in model tests.
RAOs, while robust for initial design, may not capture the nuances of every operational configuration.

b. Inaccurate in Real-Time

Once the vessel leaves the design mode or when sea states deviate from the forecast, the RAO-based specs might be at odds with reality.
This can lead to premature operational stops or, worse, operations that proceed under inaccurate assumptions.

c. Reactive Decision-Making

Traditional RAOs give you a static picture. They do not inherently provide near-future predictions that could help the crew plan lifts, gangway transfers, or DP (dynamic positioning) tasks with a proactive mindset.

 

3. Why Now? New Technology & Data-Driven Insights

“In an era of Digital Twins, Real-Time Wave and Current measurements, and IoT-enabled sensors, depending solely on RAO-based specs can feel like using a paper map in a world with GPS.”

“Today’s real-time measurement systems—such as Miros’s PredictifAI®—capture actual sea conditions and vessel motion data, then run predictive analytics to forecast vessel behavior minutes into the future. This live lens on vessel performance doesn’t just match the static RAO approach—it has the power to radically transform and refine it.”

Real-Time Adaptation

Traditional RAOs give you a static picture. They do not inherently provide near-future predictions that could help the crew plan lifts, gangway transfers, or DP (dynamic positioning) tasks with a proactive mindset.

Dynamic Operability Envelopes

Instead of a single, static envelope, operators can work with dynamic operability specs that shift with changing wave states, heading, or vessel configuration, often extending operational windows safely.

Predictive Foresight

Forecasting wave impacts and vessel responses up to two minutes in advance is a game-changer for scheduling critical operations—like hooking up cargo or moving personnel—when the vessel is most stable.